Ulster Unionist leader Robin Swann has rebuffed a suggestion that his party could merge with the DUP.
Mr Swann said unionism in Northern Ireland could not be seen as a homogenous group and that many differences remained between the two parties.
He was responding to a question from Labour MP Kate Hoey, who asked during a meeting of the Northern Ireland Affairs Committee on Tuesday if the UUP and DUP would consider joining forces as one party.
"A merger with the DUP? No. Unionism in Northern Ireland has its different outlooks. To see unionism as one homogenous group in Northern Ireland doesn't work," said Mr Swann.
He said that both parties have different outlooks on a number of issues, including social issues such as abortion and same-sex marriage.
Mr Swann said the issues of abortion and same-sex marriage were a "matter of conscience, not something that should be dictated".
"There are quite a number of differences between us", he added.
Mr Swann also said he believed that DUP leader Arlene Foster handed Sinn Fein's Michelle O'Neill a draft powersharing agreement days before the Stormont talks collapsed.
The former powersharing partners disagree on whether a draft deal existed before talks broke down.
Mrs O'Neill has claimed Mrs Foster gave it to her in person on February 9.
Mrs Foster has insisted no agreement was ever reached.
However, Mr Swann said: "I think I am pretty sure in my head it was an agreement between two parties."